The present invention relates to a shrinkable copolyester film excellent in shrinking properties, i.e., substantially free from distortion of film, wrinkle of film and uneven shrink after and at the time of shrinking.
Recently, a shrinkable polyester film has become noted because of its potential for solving the problems in the art such as problems in combustion at the time of disposal of films and recovery of films labelled on a polyethylene terephthalate (PET) bottle.
However, the conventional shrinkable polyester film is not sufficient for practical use because distortion and wrinkle appear frequently after shrinking due to precipitous occurrence of shrinking and remarkable lowering of remaining shrinkage stress.
The present inventors have proposed various methods for improving the shrinking properties of shrinkable polyester films in order to solve the above problems. The shrinking properties of the film have been improved to some extents, but still insufficient for practical use.
Especially, when the above film is applied as a label on the PET bottles with particular shapes, for example, rectangular PET bottles, wrinkles or distortion on the shrinked labels are very remarkable. And, the development of a shrinkable polyester film having more improved shrinking properties has been desired.
In view of the above, the present inventors have made further studies for solving the problems in the art and found that a shrinkable copolyester film having a specific glass transition temperature and specific shrinking properties is substantially free from wrinkles, distortion and uneven shrink after and at the time of shrinking and is suitable for a shrinkable label. The present invention has been accomplished based on this findings.